The sulfur content of petroleum products is continuing to be regulated to lower and lower levels throughout the world. Sulfur specifications in gasoline and diesel have been most recently reduced and future specifications will further lower the allowable sulfur content of fuel oils and heating oils. Sulfur is currently removed from petroleum feedstreams by various processes depending on the nature of the feedstream. Processes such as coking, distillation, and alkali metal dispersions are primarily used to remove sulfur from heavy feedstreams, such as bitumens which are complex mixtures and typically contain hydrocarbons, heteroatoms, and metals, with carbon chains in excess of about 2,000 carbon atoms. For lighter petroleum feedstreams such as distillates, catalytic hydrodesulfurization is typically used. The sulfur species in such feedstreams span a range of molecular types from sulfides, thiols, thiophenes, benzothiophenes to dibenzothiophenes in order of decreasing hydrodesulfurization (HDS) reactivity. The most difficult to remove sulfur is found in sterically hindered dibenzothiophene (“DBT”) molecules such as diethyl dibenzothiophene. The space velocity, temperature and hydrogen pressures of catalytic HDS units are determined primarily by the slow reaction kinetics of these relatively minor components of the feed. These are the molecules that are typically left in the product after conventional low-pressure hydrotreating. Removing these molecules often requires higher hydrogen pressure and higher temperature (“deep desulfurization”) which leads to higher hydrogen consumption and shorter catalyst run lengths, which are costly results. Therefore it is desirable to have alternative processes that are capable of removing these refractory sulfur molecules without incurring more severe reaction conditions for catalytic hydrotreating, which could result in significant capital and energy savings.